Process for making multi-gate transistors and resulting structures

ABSTRACT

In a gate last metal gate process for forming a transistor, a dielectric layer is formed over an intermediate transistor structure, the intermediate structure including a dummy gate electrode, typically formed of polysilicon. Various processes, such as patterning the polysilicon, planarizing top layers of the structure, and the like can remove top portions of the dielectric layer, which can result in decreased control of gate height when a metal gate is formed in place of the dummy gate electrode, decreased control of fin height for finFETs, and the like. Increasing the resistance of the dielectric layer to attack from these processes, such as by implanting silicon or the like into the dielectric layer before such other processes are performed, results in less removal of the top surface, and hence improved control of the resulting structure dimensions and performance.

PRIORITY

This application is a divisional of U.S. patent application Ser. No.16/518,505, filed on Jul. 22, 2019, (now U.S. Pat. No. 10,854,471,issuing Dec. 1, 2020) and entitled “Process for Making Multi-GateTransistors and Resulting Structures;” which is a continuation of U.S.patent application Ser. No. 16/050,148, filed on Jul. 31, 2018, (nowU.S. Pat. No. 10,361,094, issued Jul. 23, 2019), and entitled “Processfor Making Multi-Gate Transistors and Resulting Structures;” which is adivisional of U.S. patent application Ser. No. 15/441,063, filed on Feb.23, 2017 (now U.S. Pat. No. 10,177,006, issued Jan. 8, 2019), andentitled “Process for Making Multi-Gate Transistors and ResultingStructures;” which application claims the benefit to U.S. ProvisionalPatent Application No. 62/428,447, filed on Nov. 30, 2016, and entitled“Process for Making Multi-Gate Transistors and Resulting Structures;”which applications are incorporated herein by reference.

BACKGROUND

As integrated circuit dimensions shrink and device densities increase,the need exists for smaller and smaller transistor structure that can bepacked more densely while still maintaining acceptable performancelevels, even at lower operating voltages and lower power consumptionrequirements. Such devices include multi-gate transistors such asfinFETs. New processes are required to manufacture such devicesefficiently and reliably.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is an example of a Fin Field-Effect Transistor (FinFET) in athree-dimensional view.

FIGS. 2 through 6, 7A-7C, 8A-8C, 9A-9C, 10A-10C, 11A-11C, 12A-12E,13A-13C, 14A-14C, and 15A-15C are cross-sectional views of intermediatestages in the manufacturing of FinFETs with interconnect structures inaccordance with some embodiments.

FIG. 16 is flow chart illustrating steps of an embodiment process.

FIG. 17 is a flow chart illustrating steps of another embodimentprocess.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, values, operations, materials,arrangements, and the like, are described below to simplify the presentdisclosure. These are, of course, merely examples and are not intendedto be limiting. Other components, values, operations, materials,arrangements, and the like, are contemplated. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

FIG. 1 illustrates an example of a fin field-effect transistor (FinFET)30 in a three-dimensional view. The FinFET 30 comprises a fin 36 on asubstrate 32. The substrate 32 includes isolation regions 34, and thefin 36 protrudes above and from between neighboring isolation regions34. A gate dielectric 38 is along sidewalls and over a top surface ofthe fin 36, and a gate electrode 40 is over the gate dielectric 38.Source/drain regions 42 and 44 are disposed in opposite sides of the fin36 with respect to the gate dielectric 38 and gate electrode 40. FIG. 1further illustrates reference cross-sections that are used in laterfigures. Cross-section A-A is across a channel, gate dielectric 38, andgate electrode 40 of the FinFET 30. Cross-section B/C-B/C isperpendicular to cross-section A-A and is along a longitudinal axis ofthe fin 36 and in a direction of, for example, a current flow betweenthe source/drain regions 42 and 44. Subsequent figures refer to thesereference cross-sections for clarity.

Embodiments discussed herein are discussed in the context of FinFETsformed using a gate-last process. Some embodiments contemplate aspectsused in planar devices, such as planar FETs.

FIGS. 2 through 16C are cross-sectional views of intermediate stages inthe manufacturing of FinFETs in accordance with an exemplary embodiment.FIGS. 2 through 6 illustrate reference cross-section A-A illustrated inFIG. 1 , except for multiple FinFETs. In FIGS. 7A through 16C, figuresending with an “A” designation are illustrated along a similarcross-section A-A; figures ending with a “B” designation are illustratedalong a similar cross-section B/C-B/C and in a first region on asubstrate; and figures ending with a “C” designation are illustratedalong a similar cross-section B/C-B/C and in a second region on asubstrate.

FIG. 2 illustrates a substrate 50. Substrate 50 may be a semiconductorsubstrate, such as a bulk semiconductor, a semiconductor-on-insulator(SOI) substrate, or the like, which may be doped (e.g., with a p-type oran n-type dopant) or undoped. The substrate 50 may be a wafer, such as asilicon wafer. Generally, an SOI substrate comprises a layer of asemiconductor material formed on an insulator layer. The insulator layermay be, for example, a buried oxide (BOX) layer, a silicon oxide layer,or the like. The insulator layer is provided on a substrate, typically asilicon or glass substrate. Other substrates, such as a multi-layered orgradient substrate may also be used. In some embodiments, thesemiconductor material of the substrate 50 may include silicon;germanium; a compound semiconductor including silicon carbide, galliumarsenic, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs,AlGaAs, GalnAs, GaInP, and/or GaInAsP; or combinations thereof.

The substrate 50 has a first region 50B and a second region 50C. Thefirst region 50B (which corresponds to subsequent figures ending in “B”)can be for forming n-type devices, such as NMOS transistors, such asn-type FinFETs. The second region 50C (which corresponds to subsequentfigures ending in “C”) can be for forming p-type devices, such as PMOStransistors, such as p-type FinFETs.

FIGS. 3 and 4 illustrate the formation of fins 52 and isolation regions54 between neighboring fins 52. In FIG. 3 fins 52 are formed in thesubstrate 50. In some embodiments, the fins 52 may be formed in thesubstrate 50 by etching trenches in the substrate 50. The etching may beany acceptable etch process, such as a reactive ion etch (RIE), neutralbeam etch (NBE), the like, or a combination thereof. The etch may beanisotropic.

In FIG. 4 an insulation material 54 is formed between neighboring fins52 to form the isolation regions 54. The insulation material 54 may bean oxide, such as silicon oxide, a nitride, the like, or a combinationthereof, and may be formed by a high density plasma chemical vapordeposition (HDP-CVD), a flowable CVD (FCVD) (e.g., a CVD-based materialdeposition in a remote plasma system and post curing to make it convertto another material, such as an oxide), the like, or a combinationthereof. Other insulation materials formed by any acceptable process maybe used. An anneal process may be performed once the insulation materialis formed. In the illustrated embodiment, the insulation material 54 issilicon oxide formed by a FCVD process. The insulating material 54 maybe referred to as isolation regions 54. As further shown in FIG. 4 , aplanarization process, such as a chemical mechanical polish (CMP), mayremove any excess insulation material 54 and form top surfaces of theisolation regions 54 and top surfaces of the fins 52 that are coplanar.

FIG. 5 illustrates the recessing of the isolation regions 54 to formShallow Trench Isolation (STI) regions 54. The isolation regions 54 arerecessed such that fins 56 in the first region 50B and in the secondregion 50C protrude from between neighboring isolation regions 54.Further, the top surfaces of the isolation regions 54 may have a flatsurface as illustrated, a convex surface, a concave surface (such asdishing), or a combination thereof. The top surfaces of the isolationregions 54 may be formed flat, convex, and/or concave by an appropriateetch. The isolation regions 54 may be recessed using an acceptableetching process, such as one that is selective to the material of theisolation regions 54. For example, a chemical oxide removal using aCERTAS® etch or an Applied Materials SICONI tool using, e.g., dilutehydrofluoric (dHF) acid may be used.

A person having ordinary skill in the art will readily understand thatthe process described with respect to FIGS. 3 through 6 is just oneexample of how fins 56 may be formed. In other embodiments, a dielectriclayer can be formed over a top surface of the substrate 50; trenches canbe etched through the dielectric layer; homo-epitaxial structures can beepitaxially grown in the trenches; and the dielectric layer can berecessed such that the homo-epitaxial structures protrude from thedielectric layer to form fins. In still other embodiments,hetero-epitaxial structures can be used for the fins. For example, thesemiconductor strips 52 in FIG. 5 can be recessed, and a materialdifferent from the semiconductor strips 52 may be epitaxially grown intheir place. In an even further embodiment, a dielectric layer can beformed over a top surface of the substrate 50; trenches can be etchedthrough the dielectric layer; hetero-epitaxial structures can beepitaxially grown in the trenches using a material different from thesubstrate 50; and the dielectric layer can be recessed such that thehetero-epitaxial structures protrude from the dielectric layer to formfins 56. In some embodiments where homo-epitaxial or hetero-epitaxialstructures are epitaxially grown, the grown materials may be in situdoped during growth, which may obviate prior and subsequentimplantations although in situ and implantation doping may be usedtogether. Still further, it may be advantageous to epitaxially grow amaterial in an NMOS region different from the material in a PMOS region.In various embodiments, the fins 56 may comprise silicon germanium(Si_(x)Ge_(1-x), where x can be between approximately 0 and 100),silicon carbide, pure or substantially pure germanium, a III-V compoundsemiconductor, a II-VI compound semiconductor, or the like. For example,the available materials for forming III-V compound semiconductorinclude, but are not limited to, InAs, AlAs, GaAs, InP, GaN, InGaAs,InAlAs, GaSb, AlSb, AlP, GaP, and the like.

In FIG. 5 , appropriate wells (not shown) may be formed in the fins 56,fins 52, and/or substrate 50. For example, a P well may be formed in thefirst region 50B, and an N well may be formed in the second region 50C.

The different implant steps for the different regions 50B and 50C may beachieved using a photoresist or other masks (not shown). For example, aphotoresist is formed over the fins 56 and the isolation regions 54 inthe first region 50B. The photoresist is patterned to expose the secondregion 50C of the substrate 50, such as a PMOS region. The photoresistcan be formed by using a spin-on technique and can be patterned usingacceptable photolithography techniques. Once the photoresist ispatterned, an n-type impurity implant is performed in the second region50C, and the photoresist may act as a mask to substantially preventn-type impurities from being implanted into the first region 50B, suchas an NMOS region. The n-type impurities may be phosphorus, arsenic, orthe like implanted in the first region to a concentration of equal to orless than 10¹⁸ cm⁻³, such as in a range from about 10¹⁷ cm⁻³ to about10¹⁸ cm⁻³. After the implant, the photoresist is removed, such as by anacceptable ashing process.

Following the implanting of the second region 50C, a photoresist isformed over the fins 56 and the isolation regions 54 in the secondregion 50C. The photoresist is patterned to expose the first region 50Bof the substrate 50, such as the NMOS region. The photoresist can beformed by using a spin-on technique and can be patterned usingacceptable photolithography techniques. Once the photoresist ispatterned, a p-type impurity implant may be performed in the firstregion 50B, and the photoresist may act as a mask to substantiallyprevent p-type impurities from being implanted into the second region,such as the PMOS region. The p-type impurities may be boron, BF2, or thelike implanted in the first region to a concentration of equal to orless than 10¹⁸ cm⁻³, such as in a range from about 10¹⁷ cm⁻³ to about10¹⁸ cm³. After the implant, the photoresist may be removed, such as byan acceptable ashing process.

After the implants of the first region 50B and the second region 50C, ananneal may be performed to activate the p-type and n-type impuritiesthat were implanted. The implantations may form a p-well in the firstregion 50B, e.g., the NMOS region, and an n-well in the second region50C, e.g., the PMOS region. In some embodiments, the grown materials ofepitaxial fins may be in situ doped during growth, which may obviate theimplantations, although in situ and implantation doping may be usedtogether.

In FIG. 6 , a dummy dielectric layer 58 is formed on the fins 56. Thedummy dielectric layer 58 may be, for example, silicon oxide, siliconnitride, a combination thereof, or the like, and may be deposited orthermally grown according to acceptable techniques. A dummy gate layer60 is formed over the dummy dielectric layer 58, and a mask layer 62 isformed over the dummy gate layer 60. The dummy gate layer 60 may bedeposited over the dummy dielectric layer 58 and then planarized, suchas by a CMP. The mask layer 62 may be deposited over the dummy gatelayer 60. The dummy gate layer 60 may be made of, for example,polysilicon, although other materials that have a high etchingselectivity from the etching of isolation regions 54 may also be used.The mask layer 62 may include, for example, silicon nitride or the like.In this example, a single dummy gate layer 60 and a single mask layer 62are formed across the first region 50B and the second region 50C. Inother embodiments, separate dummy gate layers may be formed in the firstregion 50B and the second region 50C, and separate mask layers may beformed in the first region 50B and the second region 50C.

In FIGS. 7A, 7B, and 7C, the mask layer 62 may be patterned usingacceptable photolithography and etching techniques to form masks 72 in afirst region and masks 78 in a second region. The pattern of the masks72 and 78 then may be transferred to the dummy gate layer 60 and dummydielectric layer 58 by an acceptable etching technique to form dummygates 70 in the first region 50B and dummy gates 76 in the second region50C. The dummy gates 70 and 76 cover respective channel regions of thefins 56. The dummy gates 70 and 76 may also have a lengthwise directionsubstantially perpendicular to the lengthwise direction of respectiveepitaxial fins.

In FIGS. 8A, 8B, and 8C, gate seal spacers 80 can be formed on exposedsurfaces of respective dummy gates 70 and 76 and/or fins 56. A thermaloxidation or a deposition followed by an anisotropic etch may form thegate seal spacers 80.

After the formation of the gate seal spacers 80, implants for lightlydoped source/drain (LDD) regions may be performed. Similar to theimplants discussed above in FIG. 5 , a mask, such as a photoresist, maybe formed over the first region 50B, e.g., NMOS region, while exposingthe second region 50C, e.g., PMOS region, and p-type impurities may beimplanted into the exposed fins 56 in the second region 50C. The maskmay then be removed. Subsequently, a mask, such as a photoresist, may beformed over the second region 50C while exposing the first region 50B,and n-type impurities may be implanted into the exposed fins 56 in thefirst region 50B. The mask may then be removed. The n-type impuritiesmay be the any of the n-type impurities previously discussed, and thep-type impurities may be the any of the p-type impurities previouslydiscussed. The lightly doped source/drain regions may have aconcentration of impurities of from about 10¹⁸ cm⁻³ to about 10¹⁹ cm⁻³.An anneal may be used to activate the implanted impurities.

Further in FIGS. 8A, 8B, and 8C, epitaxial source/drain regions 82 and84 are formed in the fins 56. In the first region 50B, epitaxialsource/drain regions 82 are formed in the fins 56 such that each dummygate 70 is disposed between respective neighboring pairs of theepitaxial source/drain regions 82. In some embodiments that epitaxialsource/drain regions 82 may extend into the fins 52. In the secondregion 50C, epitaxial source/drain regions 84 are formed in the fins 56such that each dummy gate 76 is disposed between respective neighboringpairs of the epitaxial source/drain regions 84. In some embodiments thatepitaxial source/drain regions 84 may extend into the fins 52.

Epitaxial source/drain regions 82 in the first region 50B, e.g., theNMOS region, may be formed by masking the second region 50C, e.g., thePMOS region, and conformally depositing a dummy spacer layer in thefirst region 50B followed by an anisotropic etch to form dummy gatespacers (not shown) along sidewalls of the dummy gates 70 and/or gateseal spacers 80 in the first region 50B. Then, source/drain regions ofthe epitaxial fins in the first region 50B are etched to form recesses.The epitaxial source/drain regions 82 in the first region 50B areepitaxially grown in the recesses. The epitaxial source/drain regions 82may include any acceptable material, such as appropriate for n-typeFinFETs. For example, if the fin 56 is silicon, the epitaxialsource/drain regions 82 may include silicon, SiC, SiCP, SiP, or thelike. The epitaxial source/drain regions 82 may have surfaces raisedfrom respective surfaces of the fins 56 and may have facets.Subsequently, the dummy gate spacers in the first region 50B areremoved, for example, by an etch, as is the mask on the second region50C.

Epitaxial source/drain regions 84 in the second region 50C, e.g., thePMOS region, may be formed by masking the first region 50B, e.g., theNMOS region, and conformally depositing a dummy spacer layer in thesecond region 50C followed by an anisotropic etch to form dummy gatespacers (not shown) along sidewalls of the dummy gates 76 and/or gateseal spacers 80 in the second region 50C. Then, source/drain regions ofthe epitaxial fins in the second region 50C are etched to form recesses.The epitaxial source/drain regions 84 in the second region 50C areepitaxially grown in the recesses. The epitaxial source/drain regions 84may include any acceptable material, such as appropriate for p-typeFinFETs. For example, if the fin 56 is silicon, the epitaxialsource/drain regions 84 may comprise SiGe, SiGeB, Ge, GeSn, or the like.The epitaxial source/drain regions 84 may have surfaces raised fromrespective surfaces of the fins 56 and may have facets. Subsequently,the dummy gate spacers in the second region 50C are removed, forexample, by an etch, as is the mask on the first region 50B.

In FIGS. 9A, 9B, and 9C, gate spacers 86 are formed on the gate sealspacers 80 along sidewalls of the dummy gates 70 and 76. The gatespacers 86 may be formed by conformally depositing a material andsubsequently anisotropically etching the material. The material of thegate spacers 86 may be silicon nitride, SiCN, a combination thereof, orthe like.

The epitaxial source/drain regions 82 and 84 and/or epitaxial fins maybe implanted with dopants to form source/drain regions, similar to theprocess previously discussed for forming lightly doped source/drainregions, followed by an anneal. The source/drain regions may have animpurity concentration of in a range from about 10¹⁹ cm⁻³ to about 10²¹cm⁻³. The n-type impurities for source/drain regions in the first region50B, e.g., the NMOS region, may be any of the n-type impuritiespreviously discussed, and the p-type impurities for source/drain regionsin the second region 50C, e.g., the PMOS region, may be any of thep-type impurities previously discussed. In other embodiments, theepitaxial source/drain regions 82 and 84 may be in situ doped duringgrowth.

In FIGS. 10A, 10B, and 10C, an ILD 88 is deposited over the structureillustrated in FIGS. 9A, 9B, and 9C. In an embodiment, ILD 88 is aflowable film formed by a flowable CVD. In some embodiments, ILD 88 isformed of a dielectric material such as Phospho-Silicate Glass (PSG),Boro-Silicate Glass (BSG), Boron-Doped Phospho-Silicate Glass (BPSG),undoped Silicate Glass (USG), or the like, and may be deposited by anysuitable method, such as CVD, or PECVD. In some embodiments, ILD 88 iscured, e.g., by annealing after deposition.

In FIGS. 11A, 11B, and 11C, a planarization process, such as a CMP, maybe performed to level the top surface of ILD 88 with the top surfaces ofthe dummy gates 70 and 76. The CMP may also remove the masks 72 and 78on the dummy gates 70 and 76. Accordingly, top surfaces of the dummygates 70 and 76 are exposed through ILD 88. In other embodiments, masks72 and 78 are removed prior to deposition of ILD 88.

FIG. 12A illustrates in greater detail a top portion of an exemplary fin56 and ILD 88 along the axis identified as BC-BC (in FIG. 1 ). Thisillustrated embodiment corresponds to a fin 56 in region 50B (i.e., afin in which one or more NMOS transistors will be formed) although theteaching applies equally to fins formed in region 50C (in which PMOStransistors will be formed). Four dummy gates 70 are illustrated (two ofwhich are shown only partially in the partial illustration of FIG. 12 ).These four dummy gates are notated as 70, 70′, 70″ and 70′″ for clarity.Although FIG. 12A illustrates the structure from a differentperspective, it is contemplated that the processes discussed in FIGS.1-11 are employed to derive the intermediate structure illustrated inFIG. 12A. One skilled in the art will recognize that multiple dummygates can be formed over a fin; whereas four dummy gates are illustratedin the cut-away of FIG. 12A, as few as one and as many as scores orhundreds of dummy gates could be formed over the fins.

In some embodiments, it is desirable to remove all or a portion of oneor more dummy gates, in a process commonly referred to as a cut polyprocess. This is not the same process as the dummy gate removal step,which will be discussed in greater detail below. Rather, this processinvolves patterning dummy gate structures, typically formed ofpolysilicon, to form conductors that will remain on the device evenafter the remainder of the dummy gate structures have been removed andreplaced with metal gates, as described below.

FIG. 12B illustrates the structure after dummy gates 70″ and 70′″ havebeen removed. As shown, a mask layer 75 is applied over dummy gates 70and 70′ to protect them and dummy gates 70″ and 70′″ are removed, e.g.,by etching them using a common polysilicon etch process such as a wetetch or a dry etch using an appropriate chemistry, such as TetraMethylAmmonium. Hydroxide (TMAH), HBr, HF, another halide etchant, or thelike, and combinations thereof, as are well known in the art. In someinstances, some or all of ILD 88 exposed to the etch process is alsoremoved, although this is not necessary for accomplishing features ofthe disclosed embodiments. In the embodiment illustrated in FIG. 12B,exposed portions of ILD 88 are etched back, leaving remaining portions89. In a next step, mask layer 75 is removed and a sacrificial material77, such as silicon nitride is deposited over the device as shown inFIG. 12C. This sacrificial material 77 fills in the voids left behind byremoved dummy gates 70″ and 70′″. Note that sacrificial material 77conforms to the topography of the underlying structure and hence doesnot provide a planar top surface. FIG. 12D illustrates the device aftera planarizing process, such as a CMP step, has been performed onsacrificial material 77 to planarize sacrificial material 77 with topsurfaces of dummy gates 70 and 70′ and ILD 88. Note that theplanarization process causes dishing of the top surface of ILD layer 88.This is an undesirable consequence because such dishing can impact theuniformity of gate height and/or fin height in the to-be-form finFETtransistor.

FIG. 12E illustrates a process for reducing or eliminating furtherdishing or erosion of ILD 88 during subsequent process steps. As shownschematically, a process 79 is performed on ILD 88 to improve a desiredetch performance of ILD 88 relative to a subsequently performed etchprocess. For instance, process 79 can increase the etch resistivity ofILD 88 to etch processes and chemistries that are subsequently appliedto remove dummy gates 70 and 70′. In one embodiment, process 79 is animplant process wherein an elemental species such as silicon isimplanted into ILD 88. While not wishing to be bound to any particularunderlying theory, it is believed that implanting silicon into ILD 88improves its etch resistivity by making a region 81 that is rich inSi—Si bonds, and further believed that such Si—Si bonds improve the etchperformance characteristics (resistance to etching) of ILD 88. It hasbeen found that temperature and implant dosage can be tuned to alter theetch rate of ILD 88 after process 79 is performed. In an embodiment,silicon is implanted at an implant energy of from about 1 keV to about80 keV to a concentration from about 1E¹³ atoms/cm² to about 1E¹⁷atoms/cm². The temperature for the implant process can range from about−60 C to about 500 C. In one embodiment, the temperature ranges fromabout 25 C to about 450 C. It is believed that a higher temperature,around 450 C, provides a higher resulting concentration of Si—Si bonds.At an implant energy of 1.1 KeV, region 81 extends from the top surfaceof ILD 88 down about 35 Angstroms. For a 2.2 KeV implant energy, region81 extends down about 54 Angstroms, and for a 3.8 KeV implant energy,region 81 extends down about 1220 Angstroms. One skilled in the art willbe able to tune the implant parameters to achieve a desired etchcharacteristic, which depends in part upon the polysilicon etch processto be subsequently performed and how likely they are to impact ILD 88.

In other embodiments, a different species or impurity could be employedto change the etch characteristics of ILD 88. Phosphorous, for instancecould be employed, as could Boron, as examples. Other elemental speciesand combinations of species are within the contemplated scope of thepresent disclosure. Other processes such as plasma treatment, annealing,curing, and the like in addition to or in lieu of process 79 are alsowithin the contemplated scope of the present disclosure.

In the above-illustrated embodiment, the ILD 88 is processed afterplanarizing sacrificial material 77, which planarizing causes some, butacceptable levels of, dishing or erosion. It is within the contemplatedscope of the disclosed embodiments that the ILD 88 could be processedbefore depositing sacrificial material 88 so that the planarizingprocess causes even less dishing of the ILD 88.

Returning to the perspective illustrated in FIGS. 2-11 , FIGS. 13A, 13,and 13C, illustrate that the dummy gates 70 (including 70 and 70′ ofFIG. 12E) and 76, gate seal spacers 80, and portions of the dummydielectric layer 58 directly underlying the dummy gates 70 and 76 areremoved in an etching step(s), so that recesses 90 are formed. ILD 88having regions 81 is minimally eroded, etched, dished or otherwiseimpacted by this etching step. Each recess 90 exposes a channel regionof a respective fin 56. Each channel region is disposed betweenneighboring pairs of epitaxial source/drain regions 82 and 84. Duringthe removal, the dummy dielectric layer 58 may be used as an etch stoplayer when the dummy gates 70 and 76 are etched. The dummy dielectriclayer 58 and gate seal spacers 80 may then be removed after the removalof the dummy gates 70 and 76.

In FIGS. 14A, 14B, and 14C, gate dielectric layers 92 and 96 and gateelectrodes 94 and 98 are formed for replacement gates. Gate dielectriclayers 92 and 96 are deposited conformally in recesses 90, such as onthe top surfaces and the sidewalls of the fins 56 and on sidewalls ofthe gate spacers 86, and on a top surface of the ILD 88. In accordancewith some embodiments, gate dielectric layers 92 and 96 comprise siliconoxide, silicon nitride, or multilayers thereof. In other embodiments,gate dielectric layers 92 and 96 include a high-k dielectric material,and in these embodiments, gate dielectric layers 92 and 96 may have a kvalue greater than about 7.0, and may include a metal oxide or asilicate of Hf, Al, Zr, La, Mg, Ba, Ti, Pb, and combinations thereof.The formation methods of gate dielectric layers 92 and 96 may includeMolecular-Beam Deposition (MBD), Atomic Layer Deposition (ALD), PECVD,and the like.

Next, gate electrodes 94 and 98 are deposited over gate dielectriclayers 92 and 96, respectively, and fill the remaining portions of therecesses 90. Gate electrodes 94 and 98 may be made of a metal-containingmaterial such as TiN, TaN, TaC, Co, Ru, Al, combinations thereof, ormulti-layers thereof. After the filling of gate electrodes 94 and 98, aplanarization process, such as a CMP, may be performed to remove theexcess portions of gate dielectric layers 92 and 96 and the material ofgate electrodes 94 and 98, which excess portions are over the topsurface of ILD 88. The resulting remaining portions of material of gateelectrodes 94 and 98 and gate dielectric layers 92 and 96 thus formreplacement gates of the resulting FinFETs. Note that, because dishingor erosion of ILD 88 is reduced, minimized or eliminated for processesafter process 79, ILD 88 has a relatively consistent height throughoutand hence the heights of resulting gate electrodes 94 and 98 arerelatively consistent and uniform between transistors and across thelength of fin(s) 56. This uniformity in gate height improves deviceperformance and reliability

The formation of the gate dielectric layers 92 and 96 may occursimultaneously such that the gate dielectric layers 92 and 96 are madeof the same materials, and the formation of the gate electrodes 94 and98 may occur simultaneously such that the gate electrodes 94 and 98 aremade of the same materials. However, in other embodiments, the gatedielectric layers 92 and 96 may be formed by distinct processes, suchthat the gate dielectric layers 92 and 96 may be made of differentmaterials, and the gate electrodes 94 and 98 may be formed by distinctprocesses, such that the gate electrodes 94 and 98 may be made ofdifferent materials. Various masking steps may be used to mask andexpose appropriate regions when using distinct processes.

In FIGS. 15A, 15B, and 15C, an ILD 100 is deposited over ILD 88. Furtherillustrated in FIGS. 15A, 15B, and 15C, contacts 102 and 104 are formedthrough ILD 100 and ILD 88 and contacts 106 and 108 are formed throughILD 100. In an embodiment, the ILD 100 is a flowable film formed by aflowable CVD method. In some embodiments, the ILD 100 is formed of adielectric material such as PSG, BSG, BPSG, USG, or the like, and may bedeposited by any suitable method, such as CVD and PECVD. Openings forcontacts 102 and 104 are formed through the ILDs 88 and 100. Openingsfor contacts 106 and 108 are formed through the ILD 100. These openingsmay all be formed simultaneously in a same process, or in separateprocesses. The openings may be formed using acceptable photolithographyand etching techniques. A liner, such as a diffusion barrier layer, anadhesion layer, or the like, and a conductive material are formed in theopenings. The liner may include titanium, titanium nitride, tantalum,tantalum nitride, or the like. The conductive material may be copper, acopper alloy, silver, gold, tungsten, aluminum, nickel, or the like. Aplanarization process, such as a CMP, may be performed to remove excessmaterial from a surface of the ILD 100. The remaining liner andconductive material form contacts 102 and 104 in the openings. An annealprocess may be performed to form a silicide at the interface between theepitaxial source/drain regions 82 and 84 and the contacts 102 and 104,respectively. Contacts 102 are physically and electrically coupled tothe epitaxial source/drain regions 82, contacts 104 are physically andelectrically coupled to the epitaxial source/drain regions 84, contact106 is physically and electrically coupled to the gate electrode 94, andcontact 108 is physically and electrically coupled to the gate electrode98.

Although not explicitly shown, a person having ordinary skill in the artwill readily understand that further processing steps may be performedon the structure in FIGS. 15A, 15B, and 15C. For example, various IMDsand their corresponding metallization may be formed over ILD 100.

FIG. 16 is a flow chart illustrating steps of a process for anembodiment. Starting with Step 160, a fin structure extending from asubstrate and surrounded by an isolation layer, is formed. In step 161,a polysilicon layer is deposited over the fin structure. The polysiliconlayer is patterned to form a plurality of dummy structures including adummy gate structure extending over the fin structure, in step 162. Step163 includes forming a source region in the fin adjacent a first side ofthe dummy gate structure and a drain region in the fin adjacent a secondside of the dummy gate structure. An ILD is deposited over the finstructure and the dummy gate structure in step 164. Then, in step 165, aportion of the dummy structures to form recesses, a fill material isdeposited in the recesses and over the dummy gate structures, per step166. Step 167 involves processing the ILD to increase its resistance toa predetermined etch process. In step 168, the fill material isplanarized to expose the dummy gate structure. The predetermined etchprocess is then performed to remove the dummy gate structure, and ametal gate is formed in its place, per step 169. Other steps preceding,succeeding or intervening the steps illustrated in FIG. 16 are alsowithin the contemplated scope of this embodiment.

FIG. 17 is a flow chart illustrating another embodiment process, whereinan intermediate transistor structure having a dummy gate structure isformed on a substrate, as described in step 170. Then a dielectric layeris deposited over the transistor structure and the dummy gate structure,step 171. At least one process is performed on the dielectric layer toimprove its etch resistivity to a predetermined etch process at step172. Then at step 173, the dummy gate structure is removed using thepredetermined etch process. Other steps preceding, succeeding orintervening the steps illustrated in FIG. 17 are also within thecontemplated scope of this embodiment.

One general aspect of embodiments described herein includes a method,including: forming an intermediate transistor structure on a substrate,the intermediate transistor structure including a dummy gate structure;depositing a dielectric layer over the transistor structure and thedummy gate structure; performing at least one process on the dielectriclayer to improve a desired etch performance of the dielectric layerrelative to a predetermined etch process; and removing the dummy gatestructure using the predetermined etch process.

One general aspect of embodiments described herein includes a method,including: forming a fin structure extending from a substrate andsurrounded by an isolation layer; depositing a polysilicon layer overthe fin structure; patterning the polysilicon layer to form a pluralityof dummy structures, the dummy structures including a dummy gatestructure extending over the fin structure; forming a source region inthe fin adjacent a first side of the dummy gate structure and a drainregion in the fin adjacent a second side of the dummy gate structure;depositing an inter-level dielectric (ILD) over the fin structure andthe dummy gate structure; removing a portion of the dummy structures toform recesses; depositing a fill material in the recesses and over thedummy gate structure and the ILD; planarizing the fill material toexpose the dummy gate structure and the ILD; processing the ILD toincrease its resistance to a predetermined etch process; performing thepredetermined etch process to remove the dummy gate structure; andforming a metal gate structure in place of the removed dummy gatestructure.

One general aspect of embodiments described herein includes a transistorincluding: a fin structure extending from a substrate and extendingalong a major surface of the substrate in a first direction; a metalgate extending along the major surface of the substrate in a seconddirection orthogonal to the first direction, the metal gate extendingover a top surface and sidewalls of the fin structure; an inter-leveldielectric (ILD) layer over the fin structure, the ILD layer having anopening therein in which the metal gate is formed; and a processedregion in the ILD layer, the processed region extending from a topmostsurface of the ILD layer into the ILD layer, the processed region beinga silicon-silicon bond rich region of a silicon oxide material.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a fin structureextending from a substrate; forming a first dummy gate on the finstructure; depositing an inter-level dielectric (ILD) layer over the finstructure and the first dummy gate; removing the first dummy gate and afirst portion of the ILD layer to form a first recess, wherein aremaining portion of the ILD layer remains in the first recess;depositing a sacrificial material in the first recess; and planarizingthe sacrificial material to expose a second portion of the ILD layer,wherein after the planarizing, the sacrificial material extends alongand contacts an upper surface and sidewalls of the remaining portion ofthe ILD layer.
 2. The method of claim 1, further comprising forming amask layer over the second portion of the ILD layer and a second dummygate structure formed on the fin structure, wherein the mask layerprotects the second dummy gate structure and the second portion of theILD layer from removing the first dummy gate and the first portion ofthe ILD layer.
 3. The method of claim 2, wherein planarizing thesacrificial material planarizes the second portion of the ILD layer, thesacrificial material, and the second dummy gate structure.
 4. The methodof claim 3, wherein a top surface of the second portion of the ILD layeris concave after planarizing the sacrificial material.
 5. The method ofclaim 3, further comprising performing an implant process on the secondportion of the ILD layer after planarizing the sacrificial material. 6.The method of claim 5, wherein an elemental species comprising silicon,phosphorous, or boron is implanted into the second portion of the ILDlayer by the implant process.
 7. The method of claim 5, wherein theimplant process increases a density of silicon-silicon bonds in at leasta top portion of the second portion of the ILD layer.
 8. A method,comprising: forming a first dummy gate structure and a second dummy gatestructure on a substrate; depositing an interlayer dielectric layersurrounding the first dummy gate structure and the second dummy gatestructure; etching the first dummy gate structure and a first portion ofthe interlayer dielectric layer in a first region, wherein the seconddummy gate structure and a second portion of the interlayer dielectriclayer in a second region remain un-etched, wherein etching the firstdummy gate structure removes the first dummy gate structure, and whereinremaining portions of the interlayer dielectric layer remain in thefirst region after the etching; forming a sacrificial materialsurrounding the remaining portion of the interlayer dielectric layer;planarizing the sacrificial material; and etching the second dummy gatestructure to remove the second dummy gate structure after planarizingthe sacrificial material.
 9. The method of claim 8, wherein top surfacesof the second portion of the interlayer dielectric layer are above topsurfaces of the remaining portion of the interlayer dielectric layerafter etching the first dummy gate structure and the interlayerdielectric layer.
 10. The method of claim 8, further comprisingperforming a process on the interlayer dielectric layer to improve etchresistivity of the interlayer dielectric layer, wherein the process isperformed before forming the sacrificial material.
 11. The method ofclaim 8, further comprising performing a process on the interlayerdielectric layer to improve etch resistivity of the interlayerdielectric layer, wherein the process is performed after planarizing thesacrificial material and before etching the second dummy gate structure.12. The method of claim 11, wherein planarizing the sacrificial materialcauses dishing in top surfaces of the second portion of the interlayerdielectric layer.
 13. The method of claim 8, wherein etching the seconddummy gate structure forms first recesses in the second portion of theinterlayer dielectric layer, the method further comprising: depositinggate dielectric layers and gate electrodes in the first recesses; andplanarizing the gate dielectric layers and the gate electrodes such thattop surfaces of the gate dielectric layers and the gate electrodes arelevel with top surfaces of the second portion of the interlayerdielectric layer.
 14. The method of claim 8, further comprising forminga mask over the second portion of the interlayer dielectric layer,wherein the mask is removed before forming the sacrificial material. 15.A method comprising: forming a fin structure extending from a substratealong a major surface of the substrate in a first direction; depositingan inter-level dielectric (ILD) layer over the fin structure; etchingthe ILD layer to form a first opening in the ILD layer, wherein a firstportion of the ILD layer is un-etched, and wherein etching the ILD layerforms remaining portions of the ILD layer having top surfaces below atop surface of the first portion; depositing a fill material in thefirst opening, the fill material surrounding the remaining portions;performing an implant process on the ILD layer to increase a number ofsilicon-silicon bonds at a top surface of the ILD layer; afterdepositing the fill material, planarizing the fill material and the ILDlayer; forming a second opening in the ILD layer; and forming a gatestructure in the second opening.
 16. The method of claim 15, whereinperforming the implant process on the ILD layer reduces an etch rate ofan upper region of the ILD layer.
 17. The method of claim 15, whereinthe implant process is performed before planarizing the fill materialand the ILD layer.
 18. The method of claim 15, wherein the implantprocess is performed after planarizing the fill material and the ILDlayer.
 19. The method of claim 15, wherein the implant process isperformed at an implant energy from 1 keV to 80 keV, and wherein theimplant process is performed to a concentration from 1E¹³ atoms/cm² to1E¹⁷ atoms/cm².
 20. The method of claim 15, wherein the implant processis performed at a temperature from 25° C. to about 450° C.